Zoom and autofocus lens functions are well known and employed in a variety of applications. For example, a conventional zoom lens (i.e., any type of lens having a variable focal length) may include at least two lens components whose shape and spacing determine the focal length of the zoom lens. As an example, a mechanically compensated zoom lens for a camera may generally arrange the motion of the two components so that an image location or image plane remains constant. As another example, a zoom lens may have an objective lens, an image lens (also called an eye lens), and a field lens between the objective lens and the image lens. By moving the field lens and possibly the objective lens, the focal length of the zoom lens is varied.
One drawback of conventional zoom lenses is that they are often large and heavy, which makes it difficult to incorporate the zoom lens into a small device (e.g., a portable phone, a personal digital assistant (PDA), or a compact camera). Another drawback generally of conventional zoom lenses and also of autofocus lenses is that one or more of the lens components must be moved (e.g., mechanically repositioned within the lens group) to vary the focal length, which generally requires space and power to accommodate the movement. As an example, with the development and rapid market introduction of small cameras for cellular telephones, PDAs, and compact digital cameras, which typically have strict power requirements and are limited by their battery's capabilities, there is a clear need for an improved lens for providing zoom and/or autofocus functionality.